Aircraft propulsion unit comprising a gas turbomachine and a fuel cell and associated method

Abstract

A propulsion assembly (1) for an aircraft comprising a gas turbine engine (3), comprising a compression stage (31) and a combustion chamber (32) supplied with a compressed air flow (A) from the compression stage (31), at least one fuel cell (4) supplied by a feed air flow (FA), and an air supply device (5) for the fuel cell (4). The air supply device (5) is configured to: receive, on the one hand, a portion of the compressed air flow (A) from the compression stage (31), hereinafter "auxiliary air flow" (A2), and, on the other hand, an external air flow (B) from the environment external to the gas turbine engine (3); and mix the auxiliary air flow (A2) and the external air flow (B), so as to form a compressed feed air flow (FA) to supply the fuel cell (4). Abstract Figure: Figure 1

Description

Title of the invention: Propulsion assembly for aircraft comprising a gas turbomachine and a fuel cell and associated method Technical field

[0001] The present invention relates to the field of propulsion units used for the propulsion of an aircraft and relates in particular to a hybrid propulsion unit comprising a gas turbomachine and a fuel cell.

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various States. In particular, an ambitious standard applies both to new types of aircraft and those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work covers new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as essential complements to technological progress, aeronautical biofuels.

[0006] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. For this purpose, the invention relates to the field of aircraft comprising a propulsion unit hybrid including a fuel cell.

[0007] In a known manner, an aircraft comprises a propulsion unit to enable its movement from the acceleration of an air flow.

[0008] For this purpose, the propulsion assembly comprises a gas turbomachine comprising a propulsion member, mounted on a propulsion shaft, which converts the rotational movement into an air flow which enables the propulsion of the aircraft. To drive the rotation of the propulsion member, the turbomachine comprises successively along a longitudinal axis, one (or more) compression stage(s), a combustion chamber and one (or more) free or linked turbine stage(s). The compression stage is configured to receive an incoming air flow and compress it so as to supply the combustion chamber. The combustion, in the combustion chamber, between a fuel flow and the compressed air flow generates an exhaust air flow which drives the turbine stage in rotation to generate the thrust and / or drive the propulsion member of the aircraft (for example a rotor or a propeller) in rotation.

[0009] In the context of the decarbonization of aircraft, a so-called "hybrid" architecture is known in which the propulsion unit also includes a fuel cell which makes it possible to reduce kerosene consumption.

[0010] A fuel cell is a device for implementing an electrochemical reaction to generate electrical energy from a redox reaction. The electrical energy can then be used to power, for example, an electric propulsion machine. For this purpose, the fuel cell is powered by an oxidizing fluid, generally a flow of air or oxygen, and a reducing fluid, for example hydrogen, which circulate in a plurality of cells and react by means of a catalyst to form the electrochemical reaction and produce electrical energy.

[0011] In a known manner, the fuel cell is supplied with a flow of oxygen or pressurized air. Also, it is known to provide a compressor to supply a flow of pressurized air to the fuel cell.

[0012] However, such a compressor is heavy and bulky, which presents a significant drawback in an aeronautical context which aims to limit the mass of aircraft to limit their energy consumption and thus their environmental impact. In addition, the compressor needs to be supplied with energy to operate. Such energy is generally provided by the fuel cell itself, which limits its efficiency since it provides less energy to the other equipment of the aircraft. The autonomy of the fuel cell is also affected since it must provide more energy to power the compressor in parallel.

[0013] Also known in the prior art is an architecture in which the battery The fuel cell is powered by a flow of compressed air directly from the compression stage of the turbomachine. However, the flow of air taken from the compression stage to power the fuel cell reduces the flow rate of the air injected into the combustion chamber of the gas turbomachine, which limits its power. In other words, in such an architecture, the efficiency of the turbomachine is not optimal.

[0014] The invention thus aims to eliminate at least some of these drawbacks by proposing a hybrid propulsion unit, comprising a gas turbomachine and a fuel cell, whose efficiency is optimal, while having a limited mass. The propulsion unit according to the invention also makes it possible to maintain an optimal level of operational safety while limiting greenhouse gas emissions. PRESENTATION OF THE INVENTION

[0015] The invention relates to a propulsion assembly for an aircraft extending along an axis longitudinal, the propulsion unit comprising: • a gas turbomachine comprising at least one compression stage, a combustion chamber and at least one turbine stage so as to supply the combustion chamber with a flow of compressed air from the compression stage, the turbine stage being driven by a flow of exhaust air from the combustion chamber, the flow of compressed air circulating from upstream to downstream in the gas turbomachine along the longitudinal axis, and • at least one fuel cell configured to generate electrical energy to power at least one electrical load of the aircraft, the fuel cell being powered by a supply air flow.

[0016] The propulsion assembly is remarkable in that it comprises a device for supplying air to the fuel cell, the air supply device being configured to: • receive, on the one hand, a portion of the compressed air flow from the compression stage of the gas turbomachine, hereinafter “auxiliary air flow”, and, on the other hand, an external air flow from the environment outside the gas turbomachine, and • mix the auxiliary air flow and the outside air flow, so as to form a compressed supply air flow to feed the fuel cell.

[0017] The propulsion unit according to the invention makes it possible to supply the fuel cell with a flow of compressed air without requiring the use of a heavy and bulky external compressor. The mass of the aircraft is thus limited, which is particularly advantageous in the aeronautical field which aims to limit the consumption of fuel to limit greenhouse gas emissions. Eliminating the need for an external compressor also means that the fuel cell's autonomy is not affected, as it does not have to provide more energy to power a device in parallel with the dedicated electrical load(s).

[0018] The supply device advantageously limits the flow of air taken from the compression stage of the gas turbomachine, which makes it possible not to penalize the performance of the latter which maintains optimal efficiency. In other words, the use in part of an air flow coming from outside the gas turbomachine makes it possible to limit the energy cost of supplying air to the fuel cell. Thanks to the supply device, the supply air flow comes from a mixture between a limited part of the compressed air flow in the compression stage of the gas turbomachine and an external air flow which is not necessary for the operation of the turbomachine.

[0019] A hybrid propulsion system comprising a fuel cell which participates in the propulsion of the aircraft makes it possible to limit the fuel consumption of the aircraft and therefore makes it possible to limit its impact on the environment.

[0020] According to a preferred aspect, the air supply device is configured to drive the external air flow from the received auxiliary air flow. The supply device thus makes it possible to supply the fuel cell with a compressed air flow comprising in part an external air flow which does not come from the compression stage or from an external compressor.

[0021] In a preferred embodiment, the air supply device is a passive venturi effect device, preferably an ejector. A passive device advantageously makes it possible to dispense with, for example, an electrical power supply, which limits the energy consumption of the aircraft and increases the autonomy of the fuel cell and / or the use of any heavy and bulky batteries. An ejector allows the use of a simple device. Such a device can also be added simply and quickly to existing propulsion systems.

[0022] Preferably, the feed air flow supplied by the feed device to the fuel cell comprises a distribution between the auxiliary air flow and the outside air flow in which the quantity of outside air flow is between 50% and 150% of the quantity of auxiliary air flow. Such a distribution makes it possible to ensure a minimum sampling of air from the compression stage while being sufficient to supply the fuel cell with a compressed feed air flow by mixing it with an outside air flow. The minimum sampling of air flow from the compression stage makes it possible not to penalize the performance of the gas turbomachine, the efficiency of which is optimal.

[0023] Preferably, the gas turbomachine is fluidically connected to the device air supply upstream of the combustion chamber, which allows a fraction of the air flow to be taken, after it has been compressed in the compression stage, before it is introduced into the combustion chamber.

[0024] In one embodiment, the compression stage comprising a low-pressure compressor and a high-pressure compressor, the gas turbomachine is fluidically connected to the air supply device between the low-pressure compressor and the high-pressure compressor. Such an embodiment makes it possible to take a flow of compressed auxiliary air while minimizing the impact on the efficiency of the turbomachine.

[0025] Alternatively, the compression stage comprising a low pressure compressor and a high pressure compressor, the gas turbomachine is fluidically connected to the air supply device between the high pressure compressor and the combustion chamber, allowing the introduction into the air supply device of a high pressure auxiliary air flow to form a sufficiently compressed supply air flow for the fuel cell.

[0026] According to a preferred aspect, the external air flow comes from a ventilation air flow from a cowl of the gas turbomachine, from an air flow circulating in a nacelle of the gas turbomachine or from a device for capturing an air flow external to the gas turbomachine.

[0027] Preferably, the capture device is a dynamic or static air intake of the gas turbomachine or a device for scooping an air flow external to a nacelle of the gas turbomachine.

[0028] In one embodiment, the gas turbine engine and the fuel cell are concentric, the fuel cell being annular and extending radially outwardly to the gas turbine engine. The hybrid propulsion unit thus has a greatly reduced footprint, while comprising a fuel cell which makes it possible to supply electrical energy and thus contributes to limiting the greenhouse gas emissions of the aircraft. Such a more compact propulsion unit can also be easily mounted on different types of aircraft, unlike the hybrid propulsion units of the prior art which were very bulky.In this embodiment, the different supply systems (fuel or air for example) can be at least partially shared, which makes it possible to further limit the size while limiting the mass of the propulsion unit, which represents a significant advantage given the mass issues inherent in the aeronautical field.

[0029] Preferably, the fuel cell extends circumferentially around the periphery of the combustion chamber of the gas turbomachine, which makes it possible to mount the gas turbomachine and the fuel cell substantially at the same longitudinal position, allowing direct exchanges between the combustion chamber and the fuel cell. The compactness and mass of the propulsion unit are thus increased.

[0030] In one embodiment, the fuel cell comprising at least one water outlet configured to discharge a flow of water resulting from a redox reaction of the fuel cell, the gas turbomachine comprises a water inlet fluidly connected to the water outlet of the fuel cell, so as to humidify the flow of compressed air. Thus, it is no longer necessary to discharge the water resulting from the redox reaction of the fuel cell as was the case in the prior art. The flow of water is advantageously reused to lower the temperature in the combustion chamber, which makes it possible to optimize the flow of exhaust air and thus improve the energy efficiency of the gas turbomachine.

[0031] Preferably, the gas turbomachine is fluidically connected to the fuel cell upstream of the compression stage, so as to humidify the air flow entering the compression stage.

[0032] Preferably, the water outlet of the fuel cell is connected to the gas turbomachine by at least one radial water pipe, which allows the circulation of a direct flow of water between the compression stage and the fuel cell, making it possible to limit losses in long pipes. In addition, radial pipes have a limited length, which makes it possible to increase the compactness of the propulsion assembly.

[0033] The invention also relates to a system comprising a propulsion assembly as described above and a fuel tank, the fuel tank supplying the gas turbomachine and the fuel cell. A fuel supply from the same tank makes it possible to limit the size while limiting the mass of the propulsion assembly.

[0034] The invention also relates to an aircraft comprising at least one propulsion unit as described previously.

[0035] Finally, the invention relates to a method of using a propulsion unit as described above, the method comprising the steps of: • compress an air flow in the compression stage of the gas turbomachine, • divide the compressed air flow into a main air flow intended to supply the combustion chamber and an auxiliary air flow, • route the auxiliary air flow to the air supply device, • mix, in the air supply device, the auxiliary air flow with an external air flow so as to form a compressed supply air flow, and • route the air flow out of the air supply device power supply to the fuel cell to power it. PRESENTATION OF FIGURES

[0036] The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0037] [Fig.l] is a schematic representation of a propulsion unit according to a first embodiment of the invention.

[0038] [Fig.2] is a detailed view of the propulsion assembly according to a second form of realization of the invention.

[0039] [Fig. 3] is a schematic representation of a device for supplying the propulsion unit of [Fig. 1].

[0040] [Fig.4] is a schematic representation of a propulsion unit according to a third embodiment.

[0041] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0042] In a known manner, an aircraft comprises one or more propulsion units to enable its movement from the acceleration of an air flow.

[0043] With reference to [Fig. 1], there is shown a propulsion unit 1 for an aircraft according to one embodiment of the invention. The propulsion unit 1 extends longitudinally along an axis X and comprises a propulsion member 2, configured to participate in the propulsion of the aircraft by accelerating an air flow A circulating from upstream to downstream. The terms “upstream” and “downstream” refer to the axis X which extends from upstream to downstream of the propulsion unit 1, as shown in [Fig. 1].

[0044] The propulsion unit 1 according to the invention is called “hybrid” and comprises, as such, a gas turbomachine 3 and a fuel cell 4.

[0045] The gas turbomachine 3 comprises a propulsion shaft 30 connected to the propulsion member 2, for example via a gearbox (not shown). The gas turbomachine 3 also comprises successively along the longitudinal axis X, a compression stage 31, a combustion chamber 32 and a turbine stage 33, connected to the propulsion shaft 30. It goes without saying that the gas turbomachine 3 can comprise several compression stages 31 and / or several turbine stages 33.

[0046] In practice, the compression stage 31 is configured to receive a flow of air A, coming from outside the gas turbomachine 3, and to compress it, so as to supply the combustion chamber 32 with a flow of compressed air A. The combustion, in the combustion chamber 32, between a fuel flow Q and the compressed air flow A generates an exhaust air flow AE which drives the turbine stage 33 in rotation to generate the thrust of the aircraft. The rotation of the turbine stage 33 drives the rotation of the propulsion shaft 30 which in turn drives the compression stage 31 and the propulsion member 2.

[0047] To supply the combustion chamber 32, the aircraft comprises a tank R of fuel Q, shown in [Fig.2]. In this example, the fuel Q is di-hydrogen. It goes without saying that the fuel could be different, for example methane or kerosene.

[0048] As described previously, the air flow A preferably circulates substantially from upstream to downstream in the gas turbomachine 3. In practice, with reference to [Fig. 2], the air flow A is configured to circulate between the compression stage 31 and the combustion chamber 32, via an inlet channel 34 of the combustion chamber 32.

[0049] More specifically, according to one aspect of the invention, the air flow A entering the gas turbomachine 3 and compressed in the compression stage 31 is configured to be divided, at the outlet of the compression stage 31, into a main air flow A1 and an auxiliary air flow A2. The main air flow A1 is intended to supply the combustion chamber 32, via the inlet channel 34. The auxiliary air flow A2 is intended to participate in supplying the fuel cell 4, as will be described in more detail later. In this example, the gas turbomachine 3 comprises an air outlet 35 to allow the auxiliary air flow A2 to be taken.

[0050] Preferably, as shown in [Fig.2], the air outlet 35 is positioned downstream of the compression stage 31 and upstream of the combustion chamber 32, so as to take a flow of air coming directly from the compression stage 31.

[0051] More precisely, as is known, the compression stage 31 generally comprises successively along the longitudinal axis X, a low pressure compressor 31B and a high pressure compressor 31H, so as to efficiently compress the air flow A before supplying the combustion chamber 32.

[0052] In a first embodiment (not shown), the air outlet 35 is positioned between the low pressure compressor 31B and the high pressure compressor 31H, so as to take the compressed auxiliary air flow A2 while minimizing the impact on the efficiency of the gas turbomachine 3.

[0053] In a second embodiment, shown in [Fig.2], the air outlet 35 is positioned between the high pressure compressor 31H and the combustion chamber 32. In other words, the air outlet 35 is mounted in the inlet channel 34 of the combustion chamber 32, which makes it possible to take a highly compressed auxiliary air flow A2.

[0054] In a third embodiment (not shown), the air outlet 35 is mounted at a bleed valve 31V (shown in [Fig.2]) of the gas turbomachine 3. As is known, such a bleed valve 31V is mounted between the low pressure compressor 31B and the high pressure compressor 31H and is configured to evacuate a portion of the compressed air flow A in the low pressure compressor 31B, so as to control the compressed air flow A entering the combustion chamber 32, in order to optimize the bypass ratio of the gas turbomachine 3.

[0055] A single air outlet 35 is described, however, it goes without saying that the gas turbomachine 3 could alternatively comprise several air outlets 35, to allow an auxiliary air flow A2 for example coming from both the low pressure compressor 31B and the high pressure compressor 35H.

[0056] As described previously, the auxiliary air flow A2 is intended to supply a fuel cell 4.

[0057] The fuel cell 4 is configured to generate electrical energy Elec to power one or more electrical load(s) of the aircraft, such as an electric propulsion machine M or an electrical network for example. In one embodiment, the electric propulsion machine M is configured to participate in the propulsion of the aircraft by transferring energy to the propulsion member 2 so as to drive it in rotation. In this embodiment, the fuel cell 4 participates in the propulsion effort and makes it possible, for example, to limit the fuel necessary for the operation of the gas turbomachine 3.

[0058] Indeed, as is known, the fuel cell 4 is a device for implementing an electrochemical reaction to generate electrical energy Elec from an oxidation-reduction reaction. For this, the fuel cell 4 is supplied by a reducing fluid and an oxidizing fluid, for example dihydrogen H2 and dioxygen O2, which circulate in a plurality of cells and react by means of a catalyst to form the electrochemical reaction and produce electrical energy Elec. In a known manner, the cells of the plurality of cells are associated together, preferably in series. As is known, the fuel cell 4 also comprises a cooling fluid circuit which is not shown in the figures.

[0059] In one embodiment, shown in [Fig. 3], the gas turbomachine 3 and the fuel cell 4 are concentric, the fuel cell 4 being annular and extending radially outwardly to the gas turbomachine 3, which makes it possible to mount a propulsion unit 1 whose size is limited. Preferably, the fuel cell 4 extends circumferentially at the periphery of the combustion chamber 32 of the gas turbomachine 3. In other words, the fuel cell 4 and the combustion chamber 32 extend at the same axial position, so as to facilitate exchanges between the fuel cell 4 and the gas turbomachine 3. It goes without saying that the fuel cell 4 could alternatively be mounted in a different position in the propulsion assembly 1. Likewise, it goes without saying that the fuel cell 4 could just as easily have a different shape, for example a parallelepiped shape.

[0060] In one embodiment, with reference to Figures 2 and 3, the fuel cell 4 comprises at least one water outlet 43 configured to discharge a flow of water H2O resulting from the oxidation-reduction reaction of the fuel cell 4. The gas turbomachine 3 comprises, in this case, preferably, one (or more) water inlet(s) 36 fluidly connected to the water outlet 43 of the fuel cell 4, so as to humidify the main air flow A1 upstream of the compression stage 31. The temperature in the combustion chamber 32 is thus advantageously lowered.

[0061] In one embodiment, the water inlet 36 is positioned upstream of the compression stage 31. In the embodiment in which the fuel cell 4 extends circumferentially at the periphery of the gas turbomachine 3, the water outlet 43 of the fuel cell 4 is preferably connected to the water inlet 36 of the gas turbomachine 3 by a radial water pipe. A radial pipe allows the circulation of a direct flow of water between the compression stage 31 and the fuel cell 4, making it possible to limit losses in long pipes. It goes without saying that the fuel cell 4 could alternatively comprise several water outlets 43 and the gas turbomachine 3, several water inlets 36, each water inlet 36 of the gas turbomachine 3 being fluidically connected respectively to a water outlet 43 of the fuel cell 4.Such an embodiment makes it possible to humidify the main air flow Al upstream of the combustion chamber 32.

[0062] To enable the implementation of the redox reaction, as described previously, the fuel cell 4 is configured to be supplied, on the one hand, by a fuel flow Q, and, on the other hand, by a compressed air flow, hereinafter “supply flow FA”.

[0063] In particular, to enable the supply of fuel Q, the fuel cell 4 comprises a fuel inlet 41 shown in [Fig. 2]. Preferably, the fuel Q is dihydrogen. In this example, the tank R of fuel Q is fluidically connected both to the combustion chamber 32 of the turbomachine 3 and to the fuel cell 4 to supply them in parallel. It goes without saying that the aircraft could comprise a plurality of dedicated tanks R.

[0064] To enable the fuel cell 4 to be supplied with the feed air flow FA, the latter comprises an air inlet 42.

[0065] According to one aspect of the invention, as shown in Figures 1 and 2, the propulsion assembly 1 comprises a device 5 for supplying air to the fuel cell 4, preferably connected to the air inlet 42. The air supply device 5 is configured to supply the fuel cell 4 with the feed flow FA. For the sake of brevity, the air supply device 5 will hereinafter be referred to as “feed device 5”.

[0066] In this example, the supply device 5 is mounted between the gas turbomachine 3 and the fuel cell 4. In other words, the supply device 5 is fluidically connected both to the fuel cell 4 and to the gas turbomachine 3, preferably via the air outlet 35 which allows the auxiliary air flow A2 to be taken from the compression stage 31.

[0067] More specifically, with reference to Figures 1 and 2, the supply device 5 is configured to receive, on the one hand, the auxiliary air flow A2, corresponding to a portion of the compressed air flow A from the compression stage 31 of the gas turbomachine 3, and, on the other hand, an external air flow B from the environment outside the gas turbomachine 3. In other words, the external air flow B does not come from the compression stage 31 of the gas turbomachine 3, which advantageously makes it possible to limit the sampling in the compression stage 31. In this example, the external air flow B is taken from a ventilation air flow which circulates in a nacelle surrounding the gas turbomachine 3. The external air flow B could alternatively come from an air flow under a hood of the gas turbomachine 3 or from a device for capturing an air flow exterior, for example scoop type, static or dynamic air intake.

[0068] To allow the admission, into the supply device 5, of the auxiliary air flow A2 and the external air flow B, the latter preferably comprises a first supply inlet 51, fluidly connected to the air outlet 35 of the gas turbomachine 3, for example by a first supply channel 54 (shown in [Fig. 2]), and a second supply inlet 52, fluidly connected to the outside of the gas turbomachine 3 by a second supply channel 55 (also shown in [Fig. 2]). The supply device 5 also comprises a supply outlet 53, fluidly connected to the air inlet 42 of the fuel cell 4 to supply it.

[0069] According to one aspect of the invention, the supply device 5 is configured to mix the auxiliary air flow A2 and the external air flow B, so as to form the compressed supply air flow FA to supply the fuel cell 4. More precisely, the supply device 5 is configured to receive the auxiliary air flow A2 and the external air flow B and to compress the external air flow B from the auxiliary air flow A2 which has been previously compressed in the compression stage 31 of the gas turbomachine 3.

[0070] In practice, in this example, the auxiliary air flow A2 from the control stage pressure 31 has a first compression level, preferably between 3 and 20 kPa. The external air flow B preferably being an uncompressed air flow, for example an ambient air flow, the latter has a second compression level less than or equal to atmospheric pressure. The supply air flow FA corresponding to a mixture between the auxiliary air flow A2 and the external air flow B, has a third compression level, preferably between 1 and 3 kPa. In other words, the supply air flow FA is a compressed air flow whose pressure is lower than the pressure of the auxiliary air flow A2 coming from the compression stage 31 of the turbomachine 3, while being higher than atmospheric pressure. In practice, the supply air flow FA is compressed to a level compatible with the levels expected to supply the fuel cell 4.

[0071] In this example, the supply device 5 is configured to form the supply air flow FA from a distribution between the auxiliary air flow A2 and the external air flow B, in which the quantity of external air flow B is between 50% and 150% of the quantity of auxiliary air flow A2. Thus, only a limited quantity of the compressed air flow A in the compression stage 31 of the gas turbomachine 3 is taken, which makes it possible to maintain optimal efficiency of the gas turbomachine 3.

[0072] Preferably, the feed device 5 is a passive device, operating according to the venturi effect. A passive device has the advantage of not requiring any electrical power supply for example, which represents an energy saving. Preferably, the feed device 5 is an ejector.

[0073] For this purpose, with reference to [Fig. 4], the supply device 5 preferably comprises, successively from upstream to downstream, a convergent inlet portion 56, an intermediate portion 57 of cross section and a divergent outlet portion 58. The inlet portion 56 allows the admission of the auxiliary air flow A2 and the external air flow B and, as such, preferably comprises the first supply inlet 51 of the auxiliary air flow A2 and the second supply inlet 52 of the external air flow B. The inlet portion 56 is configured to mix the auxiliary air flow A2 and the external air flow B. In practice, the auxiliary air flow A2 is configured to be accelerated in the convergent-divergent device, which creates a pressure drop in the inlet portion 56, causing the suction of the external air flow B.The mixture of air flows A2, B is accelerated at the outlet of the inlet portion 56 and sucked into the intermediate portion 57 to be conveyed to the outlet portion 58. The latter being divergent from upstream to downstream, it fulfills a role of diffuser configured to convert the speed of the supply air flow FA into an increase in its pressure. Such a device is known to those skilled in the art and its operation will not be described in more detail in this . document.

[0074] The supply device 5 mounted between the gas turbomachine 3 and the fuel cell 4 and forming the supply air flow FA from the auxiliary air flow A2 and the external air flow B advantageously makes it possible to limit the air flow taken from the compression stage 31 of the gas turbomachine 3, while making it possible to supply the fuel cell 4 with a compressed air flow without the use of a heavy and bulky external compressor. The gas turbomachine 3 thus has optimal efficiency while partially supplying the fuel cell 4 by means of the compressed auxiliary air flow A2 which makes it possible to raise the pressure of the external air flow B to enable the fuel cell 4 to be supplied.

[0075] A method of using a propulsion unit 1 as described above will now be described, with reference to [Fig. 2]. In this example, the feed device 5 is an ejector.

[0076] The method comprises a first step E1 of introducing an air flow A into the gas turbomachine 3.

[0077] The air flow A is then compressed, in a step E2, in the compression stage 31 of the gas turbomachine 3 and divided, in a step E3, at the outlet of the compression stage 31, into a main air flow A1 and an auxiliary air flow A2.

[0078] In a step E4, the auxiliary air flow A2 is then conveyed, via the air outlet 35 of the gas turbomachine 3, to the first supply inlet 51 of the supply device 5. The auxiliary air flow A2 entering the supply device 5 then corresponds to an air flow directly compressed in the compression stage 31 of the gas turbomachine 3, which makes it possible to dispense with the addition of an external compressor. In this step, the main air flow A1 is conveyed in parallel in the inlet channel 34 to the combustion chamber 32, to supply it and cause the combustion of the fuel and therefore generate an exhaust air flow AE to drive the turbine stage 33 and thus the propulsion shaft 30 and the propulsion member 2.

[0079] In this same step E4, an external air flow B is introduced into the supply device 5 in parallel with the auxiliary air flow A2, via the second supply inlet 52. In practice, the pressurized auxiliary air flow A2 entering the supply device 5 sucks in the external air flow B by venturi effect.

[0080] In a step E5, the outside air flow B and the auxiliary air flow A2 mix in the supply device 5 to form the supply air flow FA. Thanks to the supply device 5 and the mixing of the outside air flow B and the auxiliary air flow A2 from the compression stage 31 of the gas turbomachine 3, the supply air flow FA is a compressed air flow making it possible to supply the fuel cell 4.

[0081] The feed air flow FA is then conveyed at the outlet of the air supply device 5, in a step E6, towards the fuel cell 4 to feed it.

Claims

Claims

1. Propulsion assembly (1) for an aircraft extending along a longitudinal axis (X), the propulsion assembly (1) comprising: • a gas turbomachine (3) comprising at least one compression stage (31), a combustion chamber (32) and at least one turbine stage (33) so as to supply the combustion chamber (32) with a compressed air flow (A) from the compression stage (31), the turbine stage (33) being driven by an exhaust air flow (AE) from the combustion chamber (32), the compressed air flow (A) flowing from upstream to downstream in the gas turbomachine (3) along the longitudinal axis (X), and • at least one fuel cell (4) configured to generate electrical energy (Elec) to supply at least one electrical load of the aircraft, the fuel cell (4) being supplied by a supply air flow (FA),• the propulsion assembly (1) being characterized in that it comprises an air supply device (5) for the fuel cell (4), the air supply device (5) being configured to: • receive, on the one hand, a portion of the compressed air flow (A) from the compression stage (31) of the gas turbomachine (3), hereinafter “auxiliary air flow (A2)”, and, on the other hand, an external air flow (B) from the environment external to the gas turbomachine (3), and • mix the auxiliary air flow (A2) and the external air flow (B), so as to form a compressed supply air flow (FA) to supply the fuel cell (4).,

2. Propulsion assembly (1) according to claim 1, wherein the air supply device (5) is configured to drive the external air flow (B) from the received auxiliary air flow (A2).

3. Propulsion assembly (1) according to claim 2, in which the air supply device (5) is a passive venturi effect device, preferably an ejector.

4. Propulsion assembly (1) according to one of claims 1 to 3, in which the supply air flow (FA) supplied by the supply device (5) to the fuel cell (4) comprises a distribution between the auxiliary air flow (A2) and the external air flow (B) in which the quantity of external air flow (B) is between 50% and 150% of the quantity of auxiliary air flow (A2).

5. Propulsion assembly (1) according to one of claims 1 to 4, in which the gas turbomachine (3) is fluidically connected to the air supply device (5) upstream of the combustion chamber (31).

6. Propulsion assembly (1) according to claim 5, in which the compression stage (31) comprises a low pressure compressor (31B) and a high pressure compressor (31H), the gas turbomachine (3) is fluidically connected to the fuel cell (4) between the low pressure compressor (31B) and the high pressure compressor (31H).

7. Propulsion assembly (1) according to claim 5, wherein the compression stage (31) comprising a low pressure compressor (31B) and a high pressure compressor (31H), the gas turbomachine (3) is fluidically connected to the air supply device (5) between the high pressure compressor (31H) and the combustion chamber (32).

8. Propulsion assembly (1) according to one of claims 1 to 7, in which the external air flow (B) comes from a ventilation air flow from a cowl of the gas turbomachine, from an air flow circulating in a nacelle of the gas turbomachine (3) or from a device for capturing an air flow external to the gas turbomachine (3).

9. Propulsion assembly (1) according to one of claims 1 to 8, in which the gas turbomachine (3) and the fuel cell (4) are concentric, the fuel cell (4) being annular and extending radially outwardly to the gas turbomachine (3).

10. Propulsion assembly (1) according to one of claims 1 to 9, in which the fuel cell (4) comprises at least one water outlet (43) configured to evacuate a flow of water (H2O) resulting from an oxidation-reduction reaction of the fuel cell (4), the gas turbomachine (3) comprises a water inlet (36) fluidly connected to the water outlet (43) of the fuel cell (4), so as to humidify the flow of compressed air (A).

11. System comprising a propulsion unit according to one of claims 1 to 10 and a fuel tank (R), the fuel tank (R) supplying the gas turbomachine (3) and the fuel cell combustible (4).

12. Aircraft comprising at least one propulsion unit (1) according to one of claims 1 to 10.

13. A method of using a propulsion unit (1) according to one of claims 1 to 10, the method comprising the steps of: • compress (E2) an air flow (A) in the compression stage (31) of the gas turbomachine (3), • divide (E3) the compressed air flow (A) into a main air flow (Al) intended to supply the combustion chamber (31) and an auxiliary air flow (A2), • route (E4) the auxiliary air flow (A2) to the air supply device (5), • mixing (E5), in the air supply device (5), the auxiliary air flow (A2) with an external air flow (B) so as to form a compressed supply air flow (FA), and • convey (E6), at the outlet of the air supply device (5), the flow of supply air (FA) to the fuel cell (4) to supply it.

Images